This invention relates to a method of detecting a weld line in which an industrial television camera advancing ahead of a welding wire along the weld line provides the video signal of the weld, the video signal thus provided is compared with a threshold value so as to be binary coded into a signal representative of the dark part of the weld and a signal representative of the bright part of the weld, the data of the dark and bright parts are subjected to difference processing to provide maximum values thereof, and the positions of the weld line and the welding wires are simultaneously or separately detected.
In order to set a welding wire accurately on the weld line, it is essential to detect the position of the weld before welding is carried out. If the detection is insufficient, then the quality of the weld may be poor. Therefore, a variety of methods have been employed to accurately detect the position of a weld line. Among the conventional methods, methods of optically detecting weld lines are extensively employed in the art. Furthermore, among these optically detecting methods, a method in which arcs at a weld are detected by light receiving elements to provide electrical signals, and the weld line is detected from the magnitudes of the electrical signals, is high in accuracy.
However, the method is still disadvantageous in resolution.